Soil Nutrient Bioavailability—A Mechanistic Approach

https://espace.library.uq.edu.au/view/UQ:7862/R103_Forrester_p.pdf

Mixed-species plantations of Eucalyptus with nitrogen-fixing trees: A review

Compaction of agricultural soils is a concern for many agricultural soil scientists and farmers since soil compaction, due to heavy field traffic, has resulted in yield reduction of most agronomic crops throughout the world. Soil compaction is a physical form of soil degradation that alters soil structure, limits water and air infiltration, and reduces root penetration in the soil. Consequences of soil compaction are still underestimated. A complete understanding of processes involved in soil compaction is necessary to meet the future global challenge of food security. We review here the advances in understanding, quantification, and prediction of the effects of soil compaction. We found the following major points: (1) When a soil is exposed to a vehicular traffic load, soil water contents, soil texture and structure, and soil organic matter are the three main factors which determine the degree of compactness in that soil. (2) Soil compaction has direct effects on soil physical properties such as bulk density, strength, and porosity; therefore, these parameters can be used to quantify the soil compactness. (3) Modified soil physical properties due to soil compaction can alter elements mobility and change nitrogen and carbon cycles in favour of more emissions of greenhouse gases under wet conditions. (4) Severe soil compaction induces root deformation, stunted shoot growth, late germination, low germination rate, and high mortality rate. (5) Soil compaction decreases soil biodiversity by decreasing microbial biomass, enzymatic activity, soil fauna, and ground flora. (6) Boussinesq equations and finite element method models, that predict the effects of the soil compaction, are restricted to elastic domain and do not consider existence of preferential paths of stress propagation and localization of deformation in compacted soils. (7) Recent advances in physics of granular media and soil mechanics relevant to soil compaction should be used to progress in modelling soil compaction.

/pdf/soil-compaction-impact-and-modelling-a-review-37n90quuou.pdf

Soil compaction impact and modelling. A review

Physiological regulation of productivity and water use in Eucalyptus: a review

https://newgenerationplantations.org/multimedia/file/e20fd847-0511-11e5-91a6-005056986313

Integrating genetic and silvicultural strategies to minimize abiotic and biotic constraints in Brazilian eucalypt plantations

Soil and stand management for short-rotation plantations.

A considerable part of eucalypt plantations in Brazil grows on low-fertility soils for which fertilization techniques and nutrient cycling processes are important to elevate and maintain the forest production. The response of these plantations to nitrogen fertilization has been relatively low, indicating that the soil has been capable of supplying part of the plant demand. Microbial biomass N is considered a readily available fraction, but little is known about the biotic and abiotic factors that affect its dynamics in eucalypt plantations in Brazil. Therefore, the objective of this work was to evaluate the variation of nitrogen in microbial biomass (NBM) of the soil and other related characteristics in seven-year-old eucalypt plantations in several soil and climatic conditions of the Brazilian Southeast. Soil samples (0-10 cm deep) were collected from March to November 1995. The NBM content ranged from 9.17 to 103.71 µg g-1, being significantly influenced by sampling time. This variation was explained by the combination of rainfall with soil C or N content. Clay content also had a strong influence on the variation. N-NH4+was the predominant form of mineral N. Carbon content and CBM (carbon of the microbial biomass) ranged from 2.78 to 12.32 g kg-1 and from 43.39 to 401.06 µg g-1, respectively. The RA (accumulated soil respiration) ranged from 14.57 to 79.42 µg g-1 and the qCO2 (metabolic quotient) ranged from 862 to 8026 µg g-1 h-1 . Unlike the C and N content, CBM was significantly influenced by sampling time. Simple linear regressions of N-NO3-, C, and N content, CBM and NBM with clay content allowed a predictive model to explain the variation of these attributes. Soil humidity explained 87% of the N-NO3- and N content variation; around 71% of the C content and 48 and 55% of the CBM and NBM variation, respectively. CBM or NBM, when considered together with C and N content, were good predictors of N mineralization.

/pdf/nitrogenio-carbono-e-atividade-da-biomassa-microbiana-do-3a3zr3u0xc.pdf

Nitrogênio, carbono e atividade da biomassa microbiana do solo em plantações de eucalipto

Predawn leaf water potential, stomatal conductance and microclimatic variables were measured on 13 sampling days from November 1995 through August 1996 to determine how environmental and physiological factors affect water use at the canopy scale in a plantation of mature clonal Eucalyptus grandis Hill ex-Maiden hybrids in the State of Espirito Santo, Brazil. The simple ”big leaf” Penman-Monteith model was used to estimate canopy transpiration. During the study period the predawn leaf water potential varied from –0.4 to –1.3 MPa, with the minimum values observed in the winter months (June and August 1996), while the average estimated values for canopy conductance and canopy transpiration fell from 17.3 to 5.8 mm s–1 and from 0.54 to 0.18 mm h–1, respectively. On the basis of all measurements, the average value of the decoupling coefficient was 0.25. During continuous soil water shortage a proportional reduction was observed in predawn leaf water potential and in daily maximum values of stomatal conductance, canopy transpiration and decoupling coefficient. The results showed that water vapour exchange in this canopy is strongly dominated by the regional vapour pressure deficit and that canopy transpiration is controlled mainly by stomatal conductance. On a seasonal basis, stomatal conductance and canopy transpiration were mainly related to predawn leaf water potential and, thus, to soil moisture and rainfall. Good results were obtained with a multiplicative empirical model that uses values of photosynthetically active radiation, vapour pressure deficit and predawn leaf water potential to estimate stomatal conductance.

Stomatal control of transpiration in the canopy of a clonal Eucalyptus grandis plantation

Nutrient use efficiency and growth of three provenances of Eucalyptus grandis and three of E. saligna were evaluated, at 78 months of age, on various sites located in the counties of Angatuba, Itapetininga, Paraibuna, Sao Miguel Arcanjo and Sao Jose dos Campos, in the state of Sao Paulo, Brazil. There was a variation in biomass production among sites, with the highest yield being obtained in Sao Miguel Arcanjo, followed by Paraibuna. The other counties constituted a third group. The genetic materials revealed variations in nutrient use efficiency from site to site. E. grandis showed greater N, P, and Mg nutrient use efficiency than E. saligna. There were no appreciable differences in efficiency between the two species for Ca and K. High nutrient use efficiency is not necessarily related to high productivity. Ca and K are the nutrients that could most limit productivity of the next rotation, when harvesting the stem. However, this limitation can be substantially reduced, especially for Ca, if only stemwood is harvested.

/pdf/eficiencia-de-utilizacao-de-nutrientes-e-sustentabilidade-da-2qi1mwircz.pdf

Eficiência de utilização de nutrientes e sustentabilidade da produção em procedências de Eucalyptus grandis e Eucalyptus saligna em sítios florestais do estado de São Paulo

Forest management practices can alter nutrient exportation from the site. The purpose of this study was to estimate nutrient contents in the aboveground biomass of eucalyptus plantations in Brazil. The influence of key climatic variables on eucalypt productivity and nutrient content was evaluated, using the database from the Reserch Programa on Soil and Eucalyptus Nutrition of the Soil Science, Departament - Federal University of Vicosa, Minas Gerais State, Brazil. Climatic characteristics were an important component of the models. In regions with low water availability the nutrient accumulation in aboveground biomass as well as biomass production were lower. The highest proportion of all nutrients (68 % N, 69 % P, 67 % K, 63 % Ca, and 68 % Mg) was accumulated in the biomass within 4.5 years after planting for harvesting after approximately 6.5 years. After 4.5 years, the potential of fertilizer response was lower. Canopy and stem bark together accounted for 65 % N, 70 % P, 64 % K, 79 % Ca, and 79 % Mg in the aboveground biomass. Debarking in the field can therefore substantially reduce nutrient exportation and contribute to a more sustainable production in eucalyptus plantations.

/pdf/alocacao-de-nutrientes-em-plantios-de-eucalipto-no-brasil-5c94g1zk7q.pdf

Nairam Félix de Barros

Papers

Soil and stand management for short-rotation plantations.

Nitrogênio, carbono e atividade da biomassa microbiana do solo em plantações de eucalipto

Stomatal control of transpiration in the canopy of a clonal Eucalyptus grandis plantation

Eficiência de utilização de nutrientes e sustentabilidade da produção em procedências de Eucalyptus grandis e Eucalyptus saligna em sítios florestais do estado de São Paulo

Alocação de nutrientes em plantios de eucalipto no Brasil